JP3542261B2 - Seam welding machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a welder, particularly a seam welder suitable for welding a fuel tank for a motorcycle.
[0002]
[Prior art]
In general, the tank body of a motorcycle fuel tank includes a body panel that forms the main body thereof, and a bottom plate that closes a lower end opening of the body panel and has an outer surface recessed inward of the panel. The first joint flange integrally formed on the outer peripheral edge of the bottom plate and the second joint flange integrally formed on the outer peripheral edge of the bottom plate are overlapped with each other to perform seam welding over the entire periphery. . Such a flange joint structure by seam welding has advantages such that high airtightness can be obtained between the body panel and the bottom plate, reliability can be improved, and workability of welding is good.
[0003]
Conventionally, as a seam welding machine used for welding such a fuel tank, for example, as shown in FIG. 8, a lower electrode wheel _RD rotatably provided on a machine frame 4 'and an upper part of the lower electrode wheel _RD lifting and rotatably provided and an upper electrode wheel R _U capable into contact or away from the lower electrode wheels R _D in each of the two electrode wheels R _D, the body panel 2 between R _U 'and a bottom plate 3' It is known that seam welding is performed with the overlapping portion of the outwardly connecting flanges 2f 'and 3f' interposed therebetween.
[0004]
[Problems to be solved by the invention]
In such a conventional seam welding machine, a lower electrode wheel R _D , an electrode support 11 ′, and a rotation driving device for lower electrode are provided on a large support frame 4 b ′ that protrudes laterally longer than the side of the machine frame 4 ′. M _D 'are mounted support, the lower electrode wheel R _D and its electrode support 11' lower has not been sufficiently open to. For this reason, the workpiece and each part of the welding machine easily interfere with each other at the time of welding, and particularly in the case of a large-sized workpiece, it is difficult to secure a wide working range in which the interference can be easily avoided and the welding can be easily performed. , Welding workability was poor.
[0005]
Further, in the structure in which the lower side of the lower electrode wheel _RD and the electrode support 11 'thereof is not widely opened as in the conventional case, the tank body 1' which is turned upside down is placed directly below the lower electrode wheel _RD at the time of welding. The welding operation is performed by placing the lower electrode wheel _RD and the electrode support 11 'in the recess 3c' with the recess 3c 'of the bottom plate 3' of the tank body 1 'facing upward. The operation to be performed is difficult because the electrode support 11 'and the support frame 4b' are in the way. Therefore, conventionally, as shown in FIG. 8, the tank body 1 'is turned sideways so that the bottom plate 3' faces the lower electrode wheel _RD , and both the joint flanges 2f ', 3f' of the body panel 2 'and the bottom plate 3' are connected. The seam welding is performed by projecting outward from the tank bottom surface. However, in such a welding method, even after welding, the two joining flanges 2f 'and 3f' are small outside the bottom surface of the tank body 1 '. In addition to this, the appearance of the tank is bad and the appearance of the tank is poor, which impairs the merchantability. In addition, the space occupied by the tank itself is increased by the outward projection of the joining flanges 2f 'and 3f'. .
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a seam welding machine having a simple structure capable of solving the above-described conventional problems.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to each claim may be configured such that a lower electrode wheel rotatably provided on a machine frame, and a lower electrode wheel rotatably provided above and below the lower electrode wheel so as to come into contact with and separate from the lower electrode wheel. An upper electrode wheel, wherein the lower electrode wheel is formed to have a smaller diameter than the upper electrode wheel, and a lower portion thereof is formed. An electrode wheel and a conductive lower electrode support rotatably supporting the electrode wheel via a conductive bearing metal are suspended from above by the machine frame so that the lower sides thereof are opened, and the lower According to this feature, the electrode support is insulated from the machine frame and connected to the current-carrying conductor. According to this feature, the size of the lower electrode wheel itself and the size of the lower electrode support that rotatably support the lower electrode wheel are reduced. And the lower electrode wheel In addition, since a sufficiently large welding work space can be secured under and on the support and on all sides (front, rear, left and right sides), the lower electrode wheel and its electrode support may be immersed in the recess of the work during welding. In addition, mutual interference between them and the work can be easily avoided, and a wide work range in which the welding work can be easily performed is ensured even when the work has a large shape, so that the welding work is facilitated and the work efficiency is improved.
[0008]
In addition, the invention of claim 2, in addition to the feature of the invention of claim 1, between the output shaft of the drive motor arranged in the machine frame above the lower electrode wheel, the lower electrode wheel, According to this feature, the drive motor is rotated as much as possible above the lower electrode wheel by interlocking rotation via a transmission mechanism provided with an insulating means for insulating between them, so that interference between the drive motor and the workpiece occurs. Can be easily avoided, and the lower electrode wheel can be accurately rotated while ensuring the insulation between the drive motor and the lower electrode wheel.
[0009]
According to a third aspect of the present invention, in addition to the features of the first or second aspect, a first joining flange portion integrally formed on a peripheral portion of a lower end opening of a body panel serving as a main body of the tank; And a second joint flange portion integrally formed on an outer peripheral edge of a bottom plate whose outer surface is closed to the lower side of the panel and closed toward the center of the lower end opening. A seam welder used for welding, wherein the lower electrode wheel and the lower electrode support are formed in a shape such that they can be immersed in a recess of the bottom plate during the seam welding. I do. According to this feature, in the case of seam welding, even when the tank body which is turned upside down is placed directly below the lower electrode wheel (therefore, the concave portion of the bottom plate of the tank body is turned upward), the center of the lower end opening of the body panel is kept. Since the welding operation of the first and second joint flanges facing each other (ie, inward) can be performed without difficulty, after welding, both joint flanges do not protrude below the tank bottom surface, and from the tank side. Disappears.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be specifically described below based on embodiments of the present invention illustrated in the accompanying drawings.
[0011]
1 to 7 show an embodiment of the present invention. In particular, FIG. 1 is a side view showing a tank body of a fuel tank and a cross-sectional view taken along line BB, and FIG. FIG. 3 is an overall side view of the seam welding machine, FIG. 4 is an overall front view of the seam welding machine (view taken in the direction of arrow 4 in FIG. 3), and FIG. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5, and FIG. 7 is a perspective view illustrating a temporary fixing process of the body panel and the bottom plate. It is.
[0012]
First, in FIGS. 1 and 2, a tank body 1 of a motorcycle fuel tank T has a dome-shaped body panel 2 which is a main body and is long in the vehicle longitudinal direction, and a lower end opening 2 a of the body panel 2 which is long in the vehicle longitudinal direction. And a bottom plate 3 whose outer surface is deeply recessed inward of the panel 2, and a fueling cylinder 3 i serving as a fueling port is fixed to the upper part of the body panel 2 by retrofitting.
[0013]
A first joint flange portion 2f is formed integrally with the peripheral edge of the lower end opening 2a of the body panel 2, and a second joint flange portion 3f is integrally formed with the outer peripheral edge of the bottom plate 3, respectively. 3f are superimposed on each other and are seam welded W over the entire circumference, whereby the airtightness of the tank T is kept good. The first and second joint flange portions 2f, 3f are formed so as to face the center of the lower end opening 2a of the body panel 2, that is, to face inward so that they cannot be seen from the side of the fuel tank T. . According to such a flange joining structure between the body panel 2 and the bottom plate 3, the joining flanges 2f and 3f do not project outward (below the tank) from the bottom surface of the tank body 1, that is, from the outside of the tank. Since the two connecting flanges 2f and 3f become invisible, the appearance of the fuel tank T is good and the commerciality can be improved. In addition, the fuel tank T can be used as much as the two connecting flanges 2f and 3f do not travel outside the tank. T itself is also reduced in size.
[0014]
Next, the structure of an embodiment of a seam welding machine for seam welding the two connecting flange portions 2f, 3f will be described with reference to FIGS. The machine frame 4 of the welding machine A has a machine frame body 4m erected on one side of the base frame 4a and a cantilever supported integrally on the upper portion of the machine frame body 4m to form an upper surface of the base frame 4a. and a support frame 4b extending horizontally so as to face, in the support frame 4b, vertically movable upper electrode wheel R _U and, the upper electrode wheel R _U upper electrode wheel as may contact or away R _U of the lower electrode wheels R _D of non lifting formed smaller in diameter than the disposed below and upper electrode wheel R _U, it is mounted in the following manner.
[0015]
A cylinder portion 5c of a telescopic cylinder 5 serving as a lifting / lowering means is vertically fixed at the center of the front end of the support frame 4b, and an upper electrode support 6 is provided at the lower end of the piston rod portion 5p of the cylinder 5. It is held together. This is the upper electrode support 6 has a horizontal upper electrode shaft 7 is rotatably fitted and supported rotation, the upper electrode wheel R _U a large diameter made of a conductive material on the tip of the shaft 7 is fixed. Thus, if the cylinder 5 is extended and contracted, the upper electrode support 6 and the upper electrode wheel _RU can be lowered and raised in accordance with the extension and contraction, and can be advanced and retracted with respect to the lower electrode wheel _RD .
[0016]
Its the machine frame main body 4m corresponding to the upper electrode shaft 7 are deployed rotary drive M _U for the upper electrode, the driving device M _U, the motor 8 _U and, the reduction mechanism leading to the motor output shaft R. An output shaft Ra of the speed reduction mechanism R is opposed to a base end of the upper electrode shaft 7, and a rotation interlock between the two shafts Ra and 7 is provided so as to allow a relative displacement in the vertical direction therebetween and integrally rotate the space therebetween. It is interlocked and connected via the mechanism I. In the illustrated example, the rotation interlocking mechanism I includes a pair of universal joints J ₁ and J ₂ and an interlocking shaft 9 connecting the two joints J ₁ and J _2. The interlocking shafts 9 are splined with each other. It is composed of a pair of shaft halves 9 ₁ and 9 _{2 that} are fitted and relatively slidable and relatively non-rotatable. When you Thus to operate the motor 8 _U, its rotation is transmitted to the deceleration to the upper electrode shaft 7 through the deceleration mechanism R and the rotation interlock mechanism I, can be slowly rotating the upper electrode wheel R _U.
[0017]
A power supply device E for power supply is accommodated in the machine frame main body 4m, and base terminals of secondary conductors L _U and L _D for current supply are connected to terminals forming a pair of the power supply device E, respectively. I have. Tip of the one of the secondary conductor L _U is connected to the upper electrode support 6 so as to conduct to the upper electrode wheel R _U, also the intermediate portion of the conductor L _U, the upper electrode support 6 Is formed so that it can be elastically deformed in accordance with the rise and fall of the shaft, and can avoid interference with the rotation interlocking mechanism I.
[0018]
A pair of left and right hanging frames 4h, 4h are integrally fixed to the tip of the support frame 4b so as to sandwich the cylinder portion 5c of the telescopic cylinder 5 from both sides thereof, and the lower ends of the hanging frames 4h, 4h are fixed. , A horizontal support frame 10 that integrally connects the components is fixed. The support frame 10 is formed with a mounting groove 10a that is open to the lower side. The groove 10a has a mounting arm 11a having a T-shaped cross section formed integrally with the upper end of the lower electrode support 11, and The flat tip portion 13 of the other secondary conductor L _D that is in contact with the upper surface of the mounting arm 11a is detachably fixed by a plurality of bolts 12 that press the mounting arm 11a from below.
[0019]
The lower electrode support 11 is entirely made of a conductive material, and has a bearing hole 11b formed in the support 11 via a bearing metal 15 formed in a cylindrical shape thinner than the conductive material. An intermediate portion of the lower electrode shaft 16 is rotatably fitted and supported, and a lower electrode wheel _RD is fixed to a tip of the shaft 16 extending from the front surface of the electrode support 11 with a plurality of bolts 17. The lower electrode wheel _RD and the lower electrode shaft 16 are also made of a conductive material. Therefore, the lower electrode wheel _RD is connected to the secondary conductor L _D through the lower electrode shaft 16, the bearing metal 15 and the lower electrode support 11. It is always in a conductive state. In addition, between the lower electrode support 11 and the tip 13 of the secondary conductor L _D and the support frame 10 is always provided by an insulating plate 18 made of a flat insulator or the like that covers the entire inner surface of the mounting groove 10a. Even if the lower electrode support 11 and the bearing metal 15 are conductive, there is no danger of a short circuit between the lower electrode wheel _RD and the machine casing 4.
[0020]
On one side of the lower electrode shaft 16, a motor 8 _D is mounted on the rear surface of the support frame 10 above the lower electrode wheel _RD, and between the motor shaft 20 of the motor 8 _D and the lower electrode shaft 16. Is provided with a reduction gear mechanism 21 as a transmission mechanism. Therefore, when the motor _8D is operated, its rotation is reduced and transmitted to the lower electrode shaft 16, whereby the lower electrode wheel _RD is slowly rotated. can, rotary drive M _D for the lower electrode is constituted by the reduction gear mechanism 21 and the motor 8 _D.
[0021]
In the illustrated example, the reduction gear mechanism 21 includes a reduction input gear 20t fixed to the motor shaft 20 and a reduction gear fixed to the base end of the lower electrode shaft 16 and meshing with the reduction input gear 20t via the intermediate gear 23t. output gear 16t and is composed of a toothing 16ta of the reduction output gear 16t are those formed by incorporating an insulating synthetic resin so as to insulate between the motor 8 _D and the lower electrode wheels R _D And constitutes the insulating means of the present invention. According to the special provision of the insulating means, even if the lower electrode support 11 and the bearing metal 15 are formed of a conductor, a short circuit between the lower electrode wheel _RD and the motor _8D (motor shaft 20) can be prevented. it can. In FIG. 6, reference numerals 30 and 31 denote thrust bearings, reference numeral 32 denotes a key for preventing rotation of the reduction output gear 16t with respect to the lower electrode shaft 16, and reference numeral 33 denotes a nut for retaining the same.
[0022]
A control panel 22 for controlling the operation of the motors 8 _U and 8 _D and the telescopic cylinder 5 and controlling the energization of the power wheels R _U and _RD by the power supply device E is provided on the side surface of the machine frame body 4 m. Will be installed.
[0023]
Next, the steps of manufacturing the tank body of the fuel tank T using the seam welding machine A of the above embodiment will be described.
[0024]
First, a metal plate is integrally formed by a conventionally known forming method (for example, press forming), and a body panel 2 and a bottom plate 3 which are main parts of the tank body 1 are separately manufactured. A first joint flange 2f is formed integrally with the peripheral edge of the lower end opening 2a, and a second joint flange 3f is formed integrally with the outer peripheral edge of the bottom plate 3. In this case, the joint flanges 2f and 3f are arranged such that they are joined together (superposed) when the bottom plate 3 is set on the body panel 2, and that the flanges 2f and 3f are not visible from the outside of the tank body 1. They are formed facing the center of the lower end opening 2a of the panel 2, that is, inward. An oiling cylinder 3i manufactured in another process is fixed to the body panel 2 by fixing means such as welding.
[0025]
Next, the bottom plate 3 is set at a fixed position in the body panel 2. At the time of this setting work, first, as shown in FIG. 7, the bottom plate 3 is inserted into the internal space of the body panel 2 which is turned upside down while tilting the bottom plate 3 forward, backward, left and right through the lower end opening 2a of the panel 2, and then By holding the bottom plate 3 using a holder (not shown) such as a suction cup, the first joint flange 2f of the panel 2 and the second joint flange 3f of the bottom plate 3 are superimposed, and the superimposed state is maintained. The bottom plate 3 is temporarily fixed to the body panel 2 so as to perform the above. At the time of this temporary fixing, conventionally known temporary fixing means used for temporarily fixing the parts to be welded at the time of welding, for example, bonding means such as adhesion, brazing, spot welding, etc. can be appropriately adopted. May be used.
[0026]
Next, the worker holds the temporarily fixed tank body 1 upside down with his / her hand and moves the tank body 1 to a position immediately below the lower electrode wheel _RD and the lower electrode support 11, and the concave portion of the bottom plate 3 of the tank body 1. The lower electrode wheel _RD and the lower electrode support 11 are immersed in 3c, and the lower surface of the second joining flange 3f of the bottom plate 3 is applied to the outer peripheral upper end of the lower electrode wheel _RD . Thereafter, the upper electrode wheel R _U is pressed against the first joint flange 2f upper surface of the body panel 2 by a telescopic cylinder 5 is extended actuated lowering the upper electrode support 6, thus, on the lower electrode wheels R _U , _RD , the overlapping portion of the two joining flanges 2f, 3f can be pressed.
[0027]
On subsequently, the rotary drive device M _U below, on to operate the motor 8 _U, 8 _D of M _D, the lower electrode wheel R _U, with synchronism with the rotation driven to the R _D their outer peripheral speed matching, both conductors from the power supply E L _U, the electrodes wheels via the L _D R _U, energizing the R _D. Along with this, the worker gradually moves the tank body 1 along the overlapping portion of the two joining flanges 2f, 3f in accordance with the rotation of the upper and lower electrode wheels R _U , R _D , whereby the two electrodes are moved. The wheels R _U and _RD roll on the corresponding two joint flanges 2f and 3f, so that the two joint flanges 2f and 3f can be seam-welded W to each other, and the weld W is formed between the two joint flanges 2f and 3f. When the operation is performed over the entire circumference, the joining between the body panel 2 and the bottom plate 3 and the assembly of the tank body 1 are completed.
[0028]
In this case, the lower electrode wheel R _D are reduced to reduce the size of the lower electrode wheels R _D itself be formed sufficiently smaller in diameter than the upper electrode wheel R _U, moreover bearing lower electrode axis 16 is a thin cylindrical It is supported by the lower electrode support 11 via the metal 15, and conduction between the lower electrode support 11 and the lower electrode shaft 16 (therefore, the lower electrode wheel R _D ) is made directly through the bearing metal 15, and accordingly, the lower electrode Since the structure of the support 11 itself is simplified and downsized, the downsized lower electrode support 11 and lower electrode wheel _RD can be easily sunk into the upward recess 3 c of the bottom plate 3. it can. Moreover, since the lower electrode support 11 is suspended and supported from above by the machine frame 4 (support frame 4b), a sufficiently wide welding is applied to all sides and lower sides of the lower electrode wheel _RD and the lower electrode support 11. A work space is ensured, and there is no possibility that the tank body 1 will interfere with each part of the welding machine A when the worker moves the tank body 1 while supporting it by hand.
[0029]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. For example, in the above-described embodiment, the welding machine A is used for seam welding of the joint portions (first and second joint flanges 2f and 3f) of the fuel tank for a motorcycle. It may be used for seam welding of a joint portion of various tank-shaped works other than the fuel tank. Further, in the above-described embodiment, when the joining flanges 2f and 3f of the tank body 1 are seam-welded to each other, the worker supports the tank body 1 by hand and moves the tank body 1 along the welding line. In the present invention, the tank body 1 may be supported by an automated feeding machine such as a robot and moved along the welding line. Further, in the above embodiment, the first joint flange 2f is formed over the entire periphery of the lower edge opening 2a of the body panel, and the second joint flange 3f is formed over the entire periphery of the outer peripheral edge of the bottom plate 3. In the present invention, the joining flanges 2f and 3f may be formed only on a part of the peripheral portion. Furthermore, a cooling fluid passage is provided in each of the electrode supports 6, 11 for forcibly circulating a coolant therein to cool the electrode supports 6, 11 and the electrode wheels R _U , R _D during welding. Oil grooves may be formed on the inner peripheral surface (bearing surface) of the bearing metal 15 to allow lubricating oil to flow, if necessary.
[0030]
【The invention's effect】
As described above, according to the invention of each claim, the lower electrode wheel is formed to have a smaller diameter than the upper electrode wheel, and the lower electrode wheel and the conductive electrode for rotatably supporting the lower electrode wheel via a conductive bearing metal. The lower electrode support is suspended from above from the machine frame so that the lower side of the lower electrode support is open, so that the lower electrode wheel itself can be downsized, and the lower electrode support that rotatably supports the lower electrode wheel can be downsized. In this way, it is possible to secure a sufficiently large welding working space below and on all sides of the lower electrode wheel and the support, and therefore, during welding, the lower electrode wheel and the support are placed in the upward recess of the work. Even when the workpiece is immersed, it is possible to accurately perform seam welding on the welded portion around the concave portion of the workpiece while easily avoiding mutual interference between the support and the workpiece and the workpiece. Wide enough to easily perform welding work Weldability working range is ensured is extremely good.
[0031]
According to the second aspect of the present invention, the drive motor provided in the machine frame for rotating and driving the lower electrode wheel can be separated as much as possible above the lower electrode wheel. Even if the support is immersed in the recess of the work, mutual interference between the work and the drive motor can be easily avoided, and even if the lower electrode support is made of a conductor, the drive motor and the lower The lower electrode wheel can be accurately driven to rotate by the motor while ensuring insulation from the electrode wheel.
[0032]
According to the third aspect of the present invention, the first joint flange portion formed integrally with the peripheral edge of the lower end opening of the body panel forming the main body of the tank, and the outer surface closing the lower end opening of the body panel is inward of the panel. In order to perform seam welding by superimposing the second joint flange portion integrally formed on the outer peripheral edge of the bottom plate recessed in the bottom plate, the tank body upside down is placed immediately below the lower electrode wheel (accordingly, the tank body With the lower electrode ring and its support immersed in the concave portion of the bottom plate, the first and second joint flanges facing the center of the lower end opening of the body panel. Welding can be performed without difficulty, and after the welding, both joint flanges do not protrude outward from the bottom of the tank and become invisible from the side of the tank. Sex can be enhanced and, moreover, is achieved also miniaturization of the tank itself.
[Brief description of the drawings]
FIG. 1 is a side view showing a tank body of a fuel tank and a cross-sectional view taken along line BB of FIG. 2. FIG. 2 is a perspective view showing a state where the tank body is turned upside down. FIG. 4 Overall front view of the seam welding machine (view from arrow 4 in FIG. 3)
FIG. 5 is an enlarged front view of a lower electrode wheel and its peripheral portion (an enlarged view as viewed from the direction of arrow 5 in FIG. 4);
6 is a sectional view taken along the line 6-6 in FIG. 5; FIG. 7 is a perspective view illustrating a temporary fixing step of the body panel and the bottom plate. FIG. 8 is a schematic view of a conventional seam welding machine, corresponding to FIG. Figure [Explanation of symbols]
R _U · · · · upper electrode wheel R _D · · · · lower electrode wheels W ----- seam welding 1 ..... tank body (work)
2 Body panel 2a Lower end opening 2f First joint flange portion (welded portion)
3 Bottom plate 3c Depressed portion 3f Second flange portion (welded portion)
4 ... Machine frame 8 _D ... Motor L _D ... Secondary conductor (conductor)
11 Lower electrode support 15 Bearing metal 16ta Reduction gears Synthetic resin teeth (insulating means)
18 Insulating plate 20 Motor shaft (output shaft)
21... Reduction gear mechanism 21 (transmission mechanism)

Claims (3)

Machine frame (4) lower electrode wheel rotatably provided (R _D), into contact or away from the upward lifting and rotatably provided in the lower electrode wheels of the lower electrode wheel (R _D) (R _D) And an upper electrode wheel (R _U ) to be obtained. Seam welding (W) is performed between the two electrode wheels (R _D , R _U ) with the welded portion (2f, 3f) of the work (1) interposed therebetween. In seam welding machines,
The lower electrode wheel (R _D ) is formed smaller in diameter than the upper electrode wheel (R _U ), and the lower electrode wheel (R _D ) and the lower electrode wheel (R _D ) are rotatable via a conductive bearing metal (15). The supporting lower electrode support (11) is suspended from above from the machine frame (4) so that the lower side thereof is opened, and the lower electrode support (11) is supported by the machine frame (11). characterized in that connected to the current supply conductor (L _D) with insulated than 4), seam welding machine. Wherein the lower electrode wheels (R _D) the machine frame (4) the output shaft of the deployed drive motor (8 _D) to be above the (20), between the lower electrode wheel (R _D), during which The seam welding machine according to claim 1, characterized in that the seam welding machine is rotated interlockingly via a transmission mechanism (21) provided with insulating means (16ta) for insulation. A first joining flange portion (2f) integrally formed with a peripheral portion of a lower end opening (2a) of a body panel (2) that forms a main body of the tank body (1); and a lower end opening (2a) of the body panel (2). And a second joint flange portion (3f) integrally formed on an outer peripheral edge of a bottom plate (3) having an outer surface recessed inward of the panel (2) toward the center of the lower end opening (2a). A seam welder used for seam welding (W) by superimposing each other in a skewing state,
The lower electrode wheel ( _RD ) and the lower electrode support (11) are formed in such a shape that they can be immersed in the recess (3c) of the bottom plate (3) during the seam welding. The seam welding machine according to claim 1, wherein the welding is performed.

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